The Fort Hood massacre ended when Sgt. Kimberly Munley spotted Maj. Nidal Malik Hasan as the alleged gunman was chasing a soldier who was already wounded and trying to shoot him again, officials said today.

Munley, the mother of two girls, came upon Hasan after rounding a corner outside the Soldiers Readiness Facility where he had wrecked havoc in a deadly rampage Thursday.

"She fired on him twice and drew the attention toward her. He immediately spun around and charged her," said Chuck Medley, director of emergency services at Fort Hood.

Munley was wounded in both legs and her wrist during the close range gunfight, but she stayed upright and kept firing at the charging gunman.

"She struck him a couple times in the upper torso and he went down," Medley said.

"When she rounded that corner she made a split-second decision to put her life at risk," he said.

"If she had not responded the way she had, we would have had an extremely high number of dead and injured," Medley said. "The number of lives that this person saved ... we will probably never know. But there is a lot of ammunition left, a lot of magazines," he said referring to what Hasan was allegedly carrying.

He said Munley was wounded in the right wrist and twice in both thighs. Medley believes the two rounds that pierced Munley's left thighs also went through her right thighs.

Lt. Gen. Robert Cone said Munley, 34, was doing traffic control in the area when Hasan allegedly began spraying unarmed soldiers with rounds from two pistols.

The civilian cop headed straight for the sound of gunfire.

"She had been trained in active response," Cone said. "They had rehearsed scenarios like this. Oftentimes, the idea is you would encircle the building and wait until you have more backup. What the belief is, if you act aggressively, to take the shooter out, you'll have less fatalities."

Munley acted aggressively, not waiting for backup. She went after the gunman and quickly found him. As Cone put it, Munley decided "to seek him out, to confront hm."

ABC News' Bob Woodruff reported today that Hasan is paralyzed from his injuries.

Medley said Munley, 34, is a former soldier who became a member of the base's civilian police department.

"She has some special qualifications," Medley said. "She's a firearms instructor. She's a member of our SWAT team...a weapons and marksman expert."

Munley's brother Daniel Barbour told ABC News at the Metroplex Hospital today that his sister has surgery Thursday night and will undergo surgery again today as one of the bullets pierced an artery.

Her husband, Matthew Munley, is a soldier at Fort Bragg, N.C., and was being flown to Fort Hood. She also has two daughters, ages 15 and 2, from a previous marriage.

Sgt. Kimberly Munley Hailed as Hero

Taken into surgery afterwards, Munley spent Thursday night calling her fellow co-workers from her hospital bed to make sure everyone was okay.

"She's doing very well," said Medley who visited Munley at 2 a.m. today. "She was in good spirits. She was smiling and laughing."

Her boss said he told Munley, "When you finally have the opportunity to lay your head on this pillow... here's what I want you to know: The action you took saved countless peoples' lives. People are healthy, alive and walking around today because of the action that this officer took. She's a hero."